994 



above sea-lcvcl. Gradual slopc with scattcred flowering piants, and 

 wind-torn strips ol' Grininiia erlcoides. The dominant species in the 

 gravel are Armeria and Ccrasliiim Edmondsloiiii; others noted: Koenigia, 

 Silene acaulis, Saxifraga stcllaris, Salix herbacea, Aira alpina, Polygonuni 

 viviparum, Kanunculus glacialis. Arabis petraea, Luzula spicata. 



8. The top o f the r o c h e s m o ii t o n n é e s n o r t h o f Thors- 

 havn (conipare p. 951 and p. 959) ; 50—75 ni. above sea-level. The tops 

 of the knoils are often denudcd and barren, with a few scattered flower- 

 ing piants: Agrostis sp., Aira alpina, Koenigia, Sagina subulata, Silene 

 acaulis, Sedum villosum, Plantago niaritima, etc. (This rocky-flat vege- 

 tation of the lower region forms a special association, diflfering from 

 the type in its components). 



The species characteristic of the rocky-flat formation may be 

 summarised as follows: Cerasfinm Edmondstonii, Silene acaulis, Ar- 

 meria, Arabis petraea, Cochlearia officinalis formå (alpina and mi- 

 cacea) , Thymus serpylhim, Koenigia, Ranunciihis acer pumila, R. 

 glacialis (seems to be absent from some islands), Alchimilla alpina, 

 Sedum villosum, Saxifraga stellaris pijgmaea, S. caespitosa, S. oppo- 

 sitifolia, Plantago maritima, Polijgonum uiuiparum, Salix herbacea, 

 Luzula spicata, Aira caespitosa brevifolia, A. alpina, Agrostis canina 

 (montana), Festuca ovina vivipara, Poa alpina vivipara, P. glauca, 

 Sagina subulata (mostly only in the lower regions); also several 

 less common species: Sagina nipalis, Juncus biglumis, J. triglumis, 

 Luzula arcuata and Saxifraga riunlaris. 



Most of these are spot-bonnd piants. The dicotyledons have 

 strong roots which strike deeply, and are thus adapted to resist 

 the assaults of the wind, whether direct in attempting to uproot 

 the piants, or indirect in removing the loose soil aroiind the plant. 



These piants are also in other respects adapted to live under 

 severe conditions. Their aerial organs are low in stature, and thus 

 offer a comparatively small surface to the wind. The same object 

 is attained when, as is frequently the case, the piants of the rocky 

 flat vary from the typical form of their species and assume a 

 dwarfed form; this is the case for example Vs'iih Cochlearia, Ranun- 

 culus acer, Plantago maritima, Saxifraga caespitosa and 5. stellaris, 

 and in a less degree with Armeria, Alchimilla alpina, Luzula spicata, 

 Aira alpina ( vivipara) , Poa alpina (vivipara) , Agrostis canina and 

 Festuca ovina (vivipara). Some species are distinclly cushion-plants 

 (»Polster-Pilanzen«): Silene acaulis (see Fig. 190), Armeria, Plantago 

 maritima and Saxifraga caespitosa. In others we find a dccumbent 

 spreading habit w^ith numerous branches which form a more or 

 less open net-w^ork exposed on the surface, partially covered over 



